Fused dithieno benzothiadiazole polymers for organic photovolatics

ABSTRACT

A method of reacting 
                         
with
 
                         
to produce
 
                         
In this method Y 1  and Y 2  are independently selected from the group consisting of: H, Cl, Br, I, and combinations thereof. Additionally in this method M is selected from the group consisting of H, trialkylstannane, boronate, or ZnX, wherein X is Cl, Br, or I. Furthermore in this method Z is a divalent linking group selected from the group consisting of:
 
                         
Lastly, in this method R 1  is selected from: H, unsubstituted or substituted branched alkyls with 1 to 60 carbon atoms or unsubstituted or substituted linear alkyls with 1 to 60 carbon atoms.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

This invention relates to polymers for organic photovoltaics.

BACKGROUND OF THE INVENTION

Solar energy using photovoltaics requires active semiconductingmaterials to convert light into electricity. Currently, solar cellsbased on silicon are the dominating technology due to their high-powerconversion efficiency. Recently, solar cells based on organic materialsshowed interesting features, especially on the potential of low cost inmaterials and processing.

Organic photovoltaic cells have many potential advantages when comparedto traditional silicon-based devices. Organic photovoltaic cells arelight weight, economical in the materials used, and can be deposited onlow-cost substrates, such as flexible plastic foils. However, organicphotovoltaic devices typically have relatively low power conversionefficiency (the ratio of incident photons to energy generated) and poorfilm forming ability.

There exists a need for a polymer to create organic photovoltaic cellsthat has high photovoltaic performance.

BRIEF SUMMARY OF THE DISCLOSURE

A method of

reacting with

to produce

In this method Y₁ and Y₂ are independently selected from the groupconsisting of: H, Cl, Br, I, and combinations thereof. Additionally inthis method M is selected from the group consisting of H,trialkylstannane, boronate, or ZnX, wherein X is Cl, Br, or I.Furthermore in this method Z is a divalent linking group selected fromthe group consisting of:

Lastly, in this method R₁ is selected from: H, unsubstituted orsubstituted branched alkyls with 1 to 60 carbon atoms or unsubstitutedor substituted linear alkyls with 1 to 60 carbon atoms.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefitsthereof may be acquired by referring to the follow description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a conventional device architecture and an inverted devicearchitecture.

FIG. 2 depicts a method of making a monomer.

FIG. 3 depicts a method of making a monomer.

FIG. 4 depicts an optional protection step when making a monomer.

FIG. 5 depicts a method of making a monomer.

FIG. 6 depicts a method of making a monomer.

FIG. 7 depicts a method of making a monomer.

FIG. 8 depicts a method of making a monomer.

FIG. 9 below describes three different polymer blends in terms of slotdie coating and thickness insensitivity.

DETAILED DESCRIPTION

Turning now to the detailed description of the preferred arrangement orarrangements of the present invention, it should be understood that theinventive features and concepts may be manifested in other arrangementsand that the scope of the invention is not limited to the embodimentsdescribed or illustrated. The scope of the invention is intended only tobe limited by the scope of the claims that follow.

“Alkyl,” as used herein, refers to an aliphatic hydrocarbon chains. Inone embodiment the aliphatic hydrocarbon chains are of 1 to about 100carbon atoms, preferably 1 to 30 carbon atoms, and includes straight andbranched chained, single, double and triple bonded carbons such asmethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,t-butyl, n-pentyl, isopentyl, neo-pentyl, n-hexyl, isohexyl, propenyl,butenyl, pentenyl, hexenyl, butadienyl, pentadienyl, hexadienyl,ethynyl, propynyl, butynyl, pentynyl, hexynyl, 2-ethylhexyl,2-butyloctyl, 2-hexyldecyl, 2-octyldedodecyl, 2-decyltetradecy and thelike. In this application alkyl groups can include the possibility ofsubstituted and unsubstituted alkyl groups. Substituted alkyl groups caninclude one or more halogen substituents.

“Alkoxy,” as used herein, refers to the group R—O— where R is an alkylgroup of 1 to 100 carbon atoms. In this application alkoxy groups caninclude the possibility of substituted and unsubstituted alkoxy groups.

“Aryl” as used herein, refers to an optionally substituted, mono-, di-,tri-, or other multicyclic aromatic ring system having from about 3 toabout 50 carbon atoms (and all combinations and subcombinations ofranges and specific numbers of carbon atoms therein), with from about 6to about 20 carbons being preferred. Non-limiting examples include, forexample, phenyl, naphthyl, anthracenyl, and phenanthrenyl. Aryl groupscan be optionally substituted with one or with one or more Rx. In thisapplication aryl groups can include the possibility of substituted arylgroups, bridged aryl groups and fused aryl groups. As used herein arylgroups also include heteroaryls, including structures with more than oneheteroatom. Non-limiting examples of heteroatoms that can be heteroarylsinclude B, N, O, Al, Si, P, S, Ge, Bi, Te, Sn, and Se. Some non-limitingexamples of aryl groups with heteroaryls include: thiophene, pyridine,pyrrole, furan, stibole, arsole selenophene, imidazole, pyrazole,oxathiole, isoxathiole, thiazole, triazole, thiadiazole, diazine,oxazine, indole, and thiazine.

“Ester”, as used herein, represents a group of formula —COOR wherein Rrepresents an “alkyl”, “aryl”, a “heterocycloalkyl” or “heteroaryl”moiety, or the same substituted as defined above

“Ketone” as used herein, represents an organic compound having acarbonyl group linked to a carbon atom such as —C(O)Rx wherein Rx can bealkyl, aryl, cycloalkyl, cycloalkenyl or heterocycle.

“Amide” as used herein, represents a group of formula“—C(O)NR^(x)R^(y),” wherein R^(x) and R^(y) can be the same orindependently H, alkyl, aryl, cycloalkyl, cycloalkenyl or heterocycle.

The present embodiment describes a composition comprising:

In this embodiment, Ar1 is independently selected from the groupconsisting of:

and Ar2 can be selected from

Furthermore R₁, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, and R₁₂ are independentlyselected from F, Cl, H, unsubstituted or substituted branched alkylswith 1 to 60 carbon atoms, and unsubstituted or substituted linearalkyls with 1 to 60 carbon atoms. In some embodiments,

is

In yet another embodiment, the composition can be A compositioncomprising:

wherein the compositional ratio of x/y ranges from about 1/99 to about99/1, and n ranges from 1 to 1,000,000. In this composition, R₁ isselected from: H, unsubstituted or substituted branched alkyls with 1 to60 carbon atoms, or unsubstituted or substituted linear alkyls with 1 to60 carbon atoms.

In other non-limiting embodiments, combinations can be contemplated suchas R₅ and R₆ are H, R₉ and R₁₀ are F, R₉ and R₁₀ are H, R₇ and R₈ areCl, or even R₇ and R₈ are F.

In these embodiments, the compositional ratio of x/y ranges from about1/99 to about 99/1, and n ranges from 1 to 1,000,000.

In other embodiments, the compositional ratio of x/y ranges from about10/90 to about 90/10, or even from about 30/70 to about 90/10.

In other embodiments, composition can comprise:

wherein the compositional ratio of x/y can be 50/50, 30/70, 90/10, oreven 60/40,

wherein the compositional ratio of x/y can be 50/50,

wherein the compositional ratio of x/y can be 80/20,

wherein the compositional ratio of x/y is 50/50,

wherein the compositional ratio of x/v is 50/50.

wherein the compositional ratio of x/y is 80/20, or even

In some embodiments, the composition can be used as a photovoltaicmaterial, an active layer material, a semi-conducting material, or evena donor material blended with an acceptor material.

In yet other embodiments, the composition is a random copolymer.

The following examples of certain embodiments of the invention aregiven. Each example is provided by way of explanation of the invention,one of many embodiments of the invention, and the following examplesshould not be read to limit, or define, the scope of the invention.

Device Architecture

When used as a photovoltaic device the architecture may be aconventional architecture device, while in others it may be an invertedarchitecture device. A conventional architecture device typicallycomprised of multilayered structure with a transparent anode as asubstrate to collect positive charge (holes) and a cathode to collectnegative charge (electrons), and a photo-active layer sandwiched inbetween two electrodes. An additional charge transport interlayer isinserted in between active layer and electrode for facile hole andelectron transport. Each charge transport layer can be consisted of oneor more layers. An inverted device has the same multilayered structureas the conventional architecture device whereas it uses a transparentcathode as a substrate to collect electrons and an anode to collectholes. The inverted device also has the photo-active layer andadditional charge transport layers sandwiched in between two electrodes.FIG. 1 depicts a conventional device architecture and an inverted devicearchitecture.

Monomers

A method wherein

is reacted with

to produce the polymer:

In this method Ar1 is independently selected from the group consistingof:

and Ar2 is selected from

In this method R₁, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independentlyselected from F, Cl, H, unsubstituted or substituted branched alkylswith 1 to 60 carbon atoms, and unsubstituted or substituted linearalkyls with 1 to 60 carbon atoms;wherein Z is a divalent linking group selected from the group consistingof:

andwherein the compositional ratio of x/y ranges from about 1/99 to about99/1, and n ranges from 1 to 1,000,000.

In an alternate embodiment, a method is taught wherein

is reacted with1,1′-(3,3′-difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane]and4,8-bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiopheneto produce the polymer:

In this polymer the compositional ratio of x/y ranges from about 1/99 toabout 99/1, and n ranges from 1 to 1,000,000 and R′ and R″ areindependently selected from: H, unsubstituted or substituted branchedalkyls with 1 to 60 carbon atoms, or unsubstituted or substituted linearalkyls with 1 to 60 carbon atoms. Furthermore, in this method R₁ isselected from F, Cl, H, unsubstituted or substituted branched alkylswith 1 to 60 carbon atoms, and unsubstituted or substituted linearalkyls with 1 to 60 carbon atoms. Additionally, in this method, Y₂ isindependently selected from Cl, Br, or I.

A method of reacting

with

to produce

In this method Y₁ and Y₂ are independently selected from the groupconsisting of: H, Cl, Br, I, and combinations thereof. Additionally inthis method M is selected from the group consisting of H,trialkylstannane, boronate, or ZnX, wherein X is Cl, Br, or I.Furthermore in this method Z is a divalent linking group selected fromthe group consisting of:

Lastly, in this method R₁ is selected from: H, unsubstituted orsubstituted branched alkyls with 1 to 60 carbon atoms or unsubstitutedor substituted linear alkyls with 1 to 60 carbon atoms.

In this method

can be further reacted to produce

Alternatively, R₁ can be selected from 2-hexyldecyl or 2-octyldodecylalkane. In other embodiments, when Y₁ is H, Y₂ is Cl, Br, I. Or when Y₂is H, Y₁ is Cl, Br, I. Furthermore, an embodiment can exist where M orY₂ is H. Such features can include when M is H, Y₂ is Cl, Br, I. Or whenY₂ is H, M is trialkylstannane, boronate, or ZnX, wherein X is Cl, Br,or I.

In some embodiments of the method,

is

is

is

In other embodiments of the method,

is

is

is

In yet further embodiments of the method,

is

is

is

In yet another embodiment of the method,

is

is

is

In other embodiments,

can be further reacted to produce

In other methods,

is

is

is

In yet more embodiments of the method,

is

is

is

In yet further embodiments of the method,

is

is

is

In even more embodiments of the method,

is

is

is

In some embodiments of the method,

is further reacted to produce

In this embodiment,

is further reacted to produce

Eventually,

can be further reacted to produce

In some embodiments,

is reacted with

to produce the polymer:

In this embodiment, Ar1 is independently selected from the groupconsisting of:

and Ar2 can be selected from

Furthermore R₁, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selectedfrom F, Cl, H, unsubstituted or substituted branched alkyls with 1 to 60carbon atoms, and unsubstituted or substituted linear alkyls with 1 to60 carbon atoms.

In some embodiments, the method does not produce

wherein Y is selected from the group consisting of Cl, Br, and I. Inother embodiments, R1 is selected from 2-hexyldecyl or2-octyldodecyl.alkane.

FIG. 2 depicts a method of preparing the following monomer

As shown in FIG. 2 , compound 2 was prepared by taking compound 1 andadding dry methylene chloride and triethylamine. Thionyl chloride isthen added and the mixture is heated. The reaction is then cooled andextracted with dichloromethane. The organic layer was dried, filtered,and concentrated. Pure fractions were concentrated to afford compound 2(10.3 mmol, 60% yield) as a tan solid.

Compound 3 of FIG. 2 is then prepared by taking compound 2 and addingdry chloroform and bromine. The reaction is then heated and then cooled.The solid was dried under vacuum to afford the product, compound 3 (1.8mmol, 93% yield).

Compound 4 of FIG. 2 is then prepared by taking compound 3 and combiningit with 2-(trimethylstannyl)-4-(2-octyldodecyl))thiophene. The reactionis then heated and reacted withtetrakis(triphenylphosphine)palladium(0). The reaction was then cooled,and the residue was dissolved in dichloromethane to obtain the desiredproduct, compound 4 (1.2 mmol, 51% yield).

Compound 5 of FIG. 2 is then prepared by taking reacting compound 4 intetrahydrofuran and treated with a solution of N-bromosuccinimide inTHF. The product, compound 5 (1.1 mmol, 76% yield), was an orange solid.

Compound 7,

is then prepared by reacting compound 3 and dry toluene. The mixture isthen mixed with tetrakis(triphenylphosphine)palladium(0) and2-(trimethylstannyl)-4-(2-octyldodecyl))thiophene. The reactioncontinues till the crude material is diluted with a mixture ofdichloromethane and chloroform. This mixture is then filtered to affordcompound 7 (0.83 mmol, 34% yield).

Compound 8,

is then prepared by reacting compound 7 and stannane,1,1′-[3″,4′-difluoro-3,3″′-bis(2-octyldodecyl)[2,2′:5′,2″:5″,2′″-quaterthiophene]-5,5′″-diyl]bis[1,1,1-trimethyl. The reaction wasthen heated and tetrakis(triphenylphosphine)palladium(0) was added toproduce compound 8 (0.091 mmol, 56% yield) as a red-violet solid.

Compound 9,

is produced by taking compound 8 and adding tetrahydrofuran andN-bromosuccinimide. This mixture produces compound 9 (0.011 mmol, 93%yield) as a red-violet solid.

In alternate embodiments, compound 5 can be created from differentreaction mechanisms. In all these reaction schemes

is not produced, where Y is Cl, Br, or I. As shown in FIG. 3 , compound5 herein labelled as compound 18 can be created from shown reactionscheme. In this reaction scheme, X is independently selected from: H,Cl, or Br. R′ can selected from: unsubstituted or substituted branchedalkyls with 1 to 60 carbon atoms, unsubstituted or substituted linearalkyls with 1 to 60 carbon atoms, C₆H₁₃, or C₁₀H₂₁. Furthermore, in thisreaction scheme, M is selected from: trialkylstannane, boronate, or ZnX,wherein the X of ZnX is selected from Cl, Br, or I. The individualreactions between the compounds can be any conventionally known reactionknown to one skilled in the art.

As a non-limiting embodiment of FIG. 3 ,1,2-di(thiophen-3-yl)ethane-1,2-dione can be added to anhydrous FeCl₃and anhydrous dichloromethane to produce compound 12. Compound 12 canthen be brominated with N-bomosuccinimide to produce compound 13.Tris(dibenzylideneacetone)dipalladium(0) and tri(o-tolyl)phosphine canthen be added to compound 13 to produce compound 14. Hydroxylaminehydrochloride can then be added to compound 14 to produce compound 15.Hydrazine monohydrate can then be added to compound 15 to producecompound 16. Thionyl chloride can then be added to compound 16 toproduce compound 17. Compound 17 can then be halogenated to producecompound 18.

As shown in FIG. 3 , compound benzo[2,1-b:3,4-b′]dithiophene-4,5-dione(1.91 g, 8.7 mmol) was added into a flask and then vacuumed and backedfilled with argon 3 times. Anhydrous dimethylformamide andN-bromosuccinimide were added. A solid (3.0 g, yield 91.5%) of product13 were obtained.

In a flask, compound 2,7-dibromobenzo[2,1-b:3,4-b′]dithiophene-4,5-dione(1 g, 2.65 mmol), tris(dibenzylideneacetone)dipalladium(0) (48.0 mg,0.053 mmol), and tri(o-tolyl)phosphine (64.0 mg, 0.212 mmol) werecombined. The crude material was dissolved in dichloromethane, adsorbedonto silica gel, and purified. Product2,7-bis(4-(2-hexyldecyl)thiophen-2-yl)benzo[2,1-b:3,4-b′]dithiophene-4,5-dione(300 mg, yield 13.6%) was obtained after the removal of solvent. A sideproduct of2-bromo-7-(4-(2-hexyldecyl)thiophen-2-yl)benzo[2,1-b:3,4-b′]dithiophene-4,5-dionewas also obtained.

Compound2,7-bis(4-(2-hexyldecyl)thiophen-2-yl)benzo[2,1-b:3,4-b′]dithiophene-4,5-dione(0.3 g, 0.36 mmol) and hydroxylamine hydrochloride (0.2 g, 2.878 mmol)were added into a flask. Analysis showed product 15 was obtained.

The previous product 15 solution (0.3 g, 0.36 mmol) was added 20 mg Pd/C(10%, 0.06 mmol). and hydrazine monohydrate (500 mg, 10 mmol) and dryethanol was added dropwise. Analysis results confirmed product 16 wereobtained.

The previous 16 crude (0.36 mmol) was vacuumed and backfilled with argonthree times before triethylamine (1.0 g, 9.8 mmol) was added. After thereaction was cooled down to room temperature, analysis results confirmedproduct 17 were obtained.

The previous 17 crude (0.36 mmol) with excess of thionyl chloride in DCMsolvent. Product 18 (120 mg, yield 35.8%) was obtained after the removalof solvent.

A solution of compound 17 (1.47 g, 1.5 mmol) in tetrahydrofuran (15 mL)was cooled to 0° C. and treated slowly with a solution ofN-bromosuccinimide (0.645 g, 3.6 mmol) in THF. The product, compound 18(1.3 g, 1.1 mmol, 76% yield), was obtained as a solid.

FIG. 4 demonstrates a protection scheme that can be used with thereaction scheme shown in FIG. 3 , or FIGS. 5-8 below to prevent theformation of

wherein Y is a halogen.

Compound 2,7-dibromobenzo[2,1-b:3,4-b′]dithiophene-4,5-dione 13 (2.5 g,6.6 mmol) was reacted with ethylene glycol (10 mL) and toluene (200 mL).Powder of mixture of 13″ and 13′ (2.9 g, yield of 94%) was obtained.

In a flask, a mixture of compounds2,7-dibromo-5H-spiro[benzo[2,1-b:3,4-b′]dithiophene-4,2′-[1,3]dioxolan]-5-oneand 13′ and2′,7′-dibromodispiro[[1,3]dioxolane-2,4′-benzo[2,1-b:3,4-b′]dithiophene-5′,2″-[1,3]dioxolane]13″ (1.1 g, 2.61 mmol), and tetrakis(triphenylphosphine)palladium(0)(150 mg, 0.13 mmol) were combined. Analysis showed mixture of product14′ and 14″.

In a flask, compound2,7-bis(4-(2-octyldodecyl)thiophen-2-yl)-5H-spiro[benzo[2,1-b:3,4-b′]dithiophene-4,2′[1,3]dioxolan]-5-one14′ (1.0 g) from previous reaction was added with acetic acid andhydrochloric acid. Analysis showed formation of product of 14.

FIG. 5 shows another reaction scheme to produce compound 5 hereinlabelled as compound 16. In this reaction scheme, the coupling reactioncan be direct arylation to produce 16. Lastly in this reaction scheme

where Y is a halogen, is not produced.

FIG. 6 shows another reaction scheme to produce compound 5 hereinlabelled as compound 15. In this reaction scheme, a coupling reactioncan be done through direct arylation to produce 12, which issubsequently reacted through methods described in this application toproduce 15. An optional SnCl₂ reduction step can be done to produce theamine intermediate while not breaking C—X bonds.

To a round bottom flask under the flow of argon compound

(0.75 g, 1.84 mmol) was added to 200-proof ethanol. A solution of SnCl₂in HCl (10 mL, 10.4 mmol) was added dropwise. The desired product

was obtained as a red solid after the removal of the solution.

FIG. 7 shows another reaction scheme to produce compound 5 hereinlabelled as compound 16. The individual reactions between the compoundsare described elsewhere and can be any conventionally known reactionknown to one skilled in the art. Lastly in this reaction scheme

is not produced, wherein Y is a halogen.

FIG. 8 shows another reaction scheme to produce compound 5 hereinlabelled as compound 17. R′ can selected from: unsubstituted orsubstituted branched alkyls with 1 to 60 carbon atoms, unsubstituted orsubstituted linear alkyls with 1 to 60 carbon atoms, C₆H₁₃, or C₁₀H₂₁.Furthermore, in this reaction scheme, M is selected from:trialkylstannane, boronate, or ZnX, wherein the X of ZnX is selectedfrom Cl, Br, or I. The individual reactions between the compounds can beany conventionally known reaction known to one skilled in the art.Lastly in this reaction scheme

is not produced, wherein Y is a halogen.

Polymer

Polymer A

wherein x/y=50/50 is produced by combining compound 5 (0.13 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.066 mmol),4,8-Bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiophene(0.066 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.005 mmol), andtri(o-tolyl)phosphine (0.021 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer A (0.13 mmol, 94%yield) was then collected.

Polymer B

wherein x/y=30/70 is produced by combining 5 (0.14 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.099 mmol),4,8-Bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiophene(0.042 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.006 mmol), andtri(o-tolyl)phosphine (0.023 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer B (0.13 mmol, 91%yield) was then collected.

Polymer C

wherein x/y=90/10 is produced by combining compound 5 (0.12 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.012 mmol),4,8-Bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiophene(0.111 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.005 mmol), andtri(o-tolyl)phosphine (0.02 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer C was then collected.

Polymer D

wherein x/y=60/40 is produced by combining compound 5 (0.088 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.035 mmol),4,8-Bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiophene(0.053 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.004 mmol), andtri(o-tolyl)phosphine (0.014 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer D (0.084 mmol, 95%yield) was then collected.

Polymer E

wherein x/y=50/50 is produced by combining compound 5 (0.13 mmol),1,1′-[2,2′-Bithiophene]-5,5′-diylbis[1,1,1-trimethylstannane] (0.066mmol),4,8-Bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiophene(0.066 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.005 mmol), andtri(o-tolyl)phosphine (0.021 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer E (0.105 mmol, 79%yield) was then collected.

Polymer F

wherein x/y=80/20 is produced by combining compound 5 (0.15 mmol),1,1′-[2,2′-Bithiophene]-5,5′-diylbis[1,1,1-trimethylstannane] (0.12mmol),1,1′-[3′-(2-Hexyldecyl)[2,2′-bithiophene]-5,5′-diyl]bis[1,1,1-trimethylstannane](0.03 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.006 mmol), andtri(o-tolyl)phosphine (0.024 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer F (0.114 mmol, 76%yield) was then collected.

Polymer G

wherein x/y=50/50 is produced by combining compound 5 (0.124 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.062 mmol),1,1′-[4,8-Bis[5-(2-ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]bis[1,1,1-trimethylstannane](0.062 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.005 mmol), andtri(o-tolyl)phosphine (0.02 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer G (0.116 mmol, 94%yield) was then collected.

Polymer H

wherein x/y=50/50 is produced by combining compound 5 (0.088 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.044 mmol),1.1′-[4,8-Bis[4-chloro-5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b′]dithiophene-2,6-diyl]bis[1,1,1-trimethylstannane](0.044 mmol), tris(dibenzylideneacetone)dipalladium(0) (3.2 mg, 0.004mmol), and tri(o-tolyl)phosphine (0.014 mmol). The reaction is heated,then cooled, then finally precipitated with methanol. Polymer H (0.084mmol, 95% yield) was then collected.

Polymer I

wherein x/y=80/20 is produced by combining compound 5 (0.097 mmol),1,1′-(3,3′-Difluoro[2,2′-bithiophene]-5,5′-diyl)bis[1,1,1-trimethylstannane](0.078 mmol),1,1′-[3′-(2-Hexyldecyl)[2,2′-bithiophene]-5,5′-diyl]bis[1,1,1-trimethylstannane](0.019 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.004 mmol), andtri(o-tolyl)phosphine (0.016 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer I (0.083 mmol, 85%yield) was then collected.

Polymer J

is produced by combining compound 9 (0.044 mmol),4,8-Bis[5-(2-ethylhexyl)thien-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b′]dithiophene(0.044 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.002 mmol), andtri(o-tolyl)phosphine (0.007 mmol). The reaction is heated, then cooled,then finally precipitated with methanol. Polymer J (0.027 mmol, 61%yield) was then collected.

Anode

When used in as an organic photovoltaic device the polymer can be usedin conjunction with an anode. The anode for the organic photovoltaicdevice can be any conventionally known anode capable of operating as anorganic photovoltaic device. Examples of anodes that can be usedinclude: indium tin oxide, aluminum, silver, carbon, graphite, graphene,PEDOT:PSS, copper, metal nanowires, Zn₉₉InO_(x), Zn₉₈In₂O_(x),Zn₉₇In₃O_(x), Zn₉₅Mg₅O_(x), Zn₉₀Mg₁₀O_(x), and Zn₈₅Mg₁₅O_(x).

Cathode

When used in as an organic photovoltaic device the polymer can be usedin conjunction with a cathode. The cathode for the organic photovoltaicdevice can be any conventionally known cathode capable of operating asan organic photovoltaic device. Examples of cathodes that can be usedinclude: indium tin oxide, carbon, graphite, graphene, PEDOT:PSS,copper, silver, aluminum, gold, metal nanowires.

Electron Transport Layer

When used in as an organic photovoltaic device the copolymer can bedeposited onto an electron transport layer. Any commercially availableelectron transport layer can be used that is optimized for organicphotovoltaic devices. In one embodiment the electron transport layer cancomprise (AO_(x))_(y)BO_((1-y)). In this embodiment, (AO_(x))_(y) andBO_((1-y)) are metal oxides. A and B can be different metals selected toachieve ideal electron transport layers. In one embodiment A can bealuminum, indium, zinc, tin, copper, nickel, cobalt, iron, ruthenium,rhodium, osmium, tungsten, magnesium, indium, vanadium, titanium andmolybdenum.

In one embodiment B can be aluminum, indium, zinc, tin, copper, nickel,cobalt, iron, ruthenium, rhodium, osmium, tungsten, vanadium, titaniumand molybdenum.

Examples of (AO_(x))_(y)BO_((1-y)) include: (SnO_(x))_(y)ZnO_((1-y)),(AlO_(x))_(y)ZnO_((1-y)), (AlO_(x))_(y)InO_(z(1-y)),(AlO_(x))_(y)SnO_(z(1-y)), (AlO_(x))_(y)CuO_(z(1-y)),(AlO_(x))_(y)WO_(z(1-y)), (InO_(x))_(y)ZnO_(z(1-y)),(InO_(x))_(y)SnO_(z(1-y)), (InO_(x))_(y)NiO_(z(1-y)),(ZnO_(x))_(y)CuO_(z(1-y)), (ZnO_(x))_(y)NiO_(z(1-y)),(ZnO_(x))_(y)FeO_(z(1-y)), (WO_(x))_(y)VO_(z(1-y)),(WO_(x))_(y)TiO_(z(1-y)), and (WO_(x))_(y)MoO_(z(1-y)).

In an alternate embodiment, various fullerene dopants can be combinedwith (AO_(x))_(y)BO_((1-y)) to make an electron transport layer for theorganic photovoltaic device. Examples of fullerene dopants that can becombined include

and [6,6]-phenyl-C₆₀-butyric-N-2-trimethylammonium ethyl ester iodide.

In the embodiment of

R′ can be selected from either N, O, S, C, or B. In other embodiment R″can be alkyl chains or substituted alkyl chains. Examples ofsubstitutions for the substituted alkyl chains include halogens, N, Br,O, Si, or S. In one example R″ can be selected from

Other examples of fullerene dopants that can be used include:[6,6]-phenyl-C₆₀-butyric-N-(2-aminoethyl)acetamide,[6,6]-phenyl-C₆₀-butyric-N-triethyleneglycol ester and[6,6]-phenyl-C₆₀-butyric-N-2-dimethylaminoethyl ester.

Organic Photovoltaic Device Fabrication

Zinc/tin oxide (ZTO):phenyl-C60-butyric-N-(2-hydroxyethyl)acetamide(PCBNOH) sol-gel solution was prepared by dissolving zinc acetatedihydrate or tin(II) acetate in 2-methoxyethanol and ethanolamine.Specifically, the ZTO:PCBNOH sol-gel electron transport layer solutionwas prepared by mixing Zn(OAc)₂ (3.98 g), Sn(OAc)₂ (398 mg) and PCBNOH(20.0 mg) in 2-methoxyethanol (54 mL) with ethanolamine (996 μL).Solutions were then further diluted to 65 vol % by adding more2-methoxyethanol and stirred for at least an hour before spin castingonto indium tin oxide substrate to form the electron transport layer.

In alternate embodiments, the formation of ZTO([6,6]-phenyl-C₆₀-butyric-N-2-trimethylammonium ethyl ester iodide(PCBNMI) can be used as well. One method of forming PCBNMI can be taking[6,6]-phenyl-C60-butyric-N-2-dimethylaminoethyl ester (0.05 g, 0.052mmol) and dissolved it in dry THF (2 mL) under argon. Iodomethane (1.5mL) was added in one portion and the vessel was sealed. The solution isthen heated to 60° C. for 18 hours. The solution was cooled and openedto allow the liquids to evaporate. The solid residue was suspended inmethanol, diluted with acetone, and centrifuged. This process wasrepeated to produce [6,6]-phenyl-C₆₀-butyric-N-2-trimethylammonium ethylester iodide as a metallic green powder (0.05 g, ˜99% yield).

The polymer and the acceptor, EH-IDTBR, in a ratio of 1:2 were dissolvedin toluene at the concentration of 27 mg/mL to obtain the photo-activelayer solution. The solution was stirred and heated at 80° C. overnightin a nitrogen filled glove box. The next day from about 0-0.5% vol % of1,8-diiodooctane (DIO) was added before spin-coating of the photo-activelayer.

Indium tin oxide patterned glass substrates were cleaned by successiveultra-sonications in acetone and isopropanol. Each 15 min step wasrepeated twice, and the freshly cleaned substrates were left to dryovernight at 60° C. Preceding fabrication, the substrates were furthercleaned for 1.5 min in a UV-ozone chamber and the electron transportlayer was immediately spin coated on top.

Sol-gel electron transport layer solution was filtered directly onto theindium tin oxide with a 0.25 μm poly(vinylidene fluoride) filter andspin cast at 4000 rpm for 40 s. Films were then annealed at 170° C. for15 min, and directly transferred into a nitrogen filled glove box.

The photo-active layer was deposited on the electron transport layer viaspin coating at 1600-4000 rpm for 40 s with the solution and thesubstrate being preheated at 80° C. and directly transferred into aglass petri dish for to be dried.

After drying, the substrates were loaded into the vacuum evaporatorwhere MoO₃ (hole transport layer) and Ag (anode) were sequentiallydeposited by thermal evaporation. Deposition occurred at a pressure of<4×10⁻⁶ torr. MoO₃ and Ag had thicknesses of 5.0 nm and 120 nm,respectively. Samples were then encapsulated with glass using an epoxybinder and treated with UV light for 3 min.

Photovoltaic Device Performance

Cyclic Voltammetry Analysis

Cyclic voltammetry (CV) experiments were performed using a 3.0 mmdiameter (7.06 mm2 area) glassy carbon working electrode, platinum coilcounter electrode, and a silver wire/0.1M AgNO3 in acetonitrilereference solution. Solutions were purged of air using Argon precedingvoltammetry measurements. Oxidation and reduction onset potentials werecalculated as the intersection of the linear fits of the baselinecurrent and the linear region of the oxidation or reduction event.Measurements with an initially positive scan direction at 100 mV/s wereobtained on all solutions. Ferrocene was used as an external standardwith an oxidation E1/2 of 0.136 V and a peak-to-peak separation ofapproximately 0.100 V. Small molecule material solutions were preparedat dilute concentrations of up to 1 mg/mL in a 0.3 M tetrabutylammoniumhexafluorophosphate dichloromethane solution. A thin polymer film wascoated from chlorobenzene onto the glassy carbon working electrode.Polymer films were measured in 0.1 M tetrabutylammoniumhexafluorophosphate acetonitrile electrolyte. The HOMO levels werecalculated from the CV oxidation onset potentials using equation 1. Thepolymer optical bandgap was derived from the onset of polymer filmUV-visible absorption by using equation 2. The lowest un-occupiedmolecular orbital (LUMO) energy was calculated using equation 3.E _(HOMO)=−[E _(ox(onset)) −E _((1/2 Ferrocene))+4.8] eVE _(Bandgap)=[1240/Onset Wavelength (nm)] eVE _(LUMO)=[E _(HOMO) +EBandgap] eV

_(Eox(onset)) and _(Ered(onset)) are the onset oxidation and reductionpotentials for the compounds against the ferrocene reference. Thevalue—4.8 eV is the HOMO energy level of ferrocene against vacuum.

Device Fabrication

Small area OPV devices were fabricated with the inverted architectureITO/ZnMOx/P:A/MoO₃/Ag.

Electron Transport Layer Deposition

Zinc tin oxide (ZTO) sol gel solutions were prepared by adding zincacetate dihydrate (996 mg), tin (II) acetate (99.6 mg) to2-methoxyethanol (10 mL) and ethanolamine (249 μL). Solutions werestirred for a minimum of 12 hours before use.

ITO patterned glass substrates were cleaned by successive 10 minutesultra-sonication in detergent (Versa-Clean), deionized water, acetone,and isopropanol. The substrates were then cleaned for 1 minute 30seconds in a UV-ozone chamber and the electron transport layer wasimmediately spin coated on the substrates. The ZTO sol gel solution wasfiltered directly onto ITO with a 0.25 μm poly(tetrafluoroethylene)filter and spin cast at 4,000 rpm for 40 seconds. Films were thenannealed at 170° C. for 20 minutes, and directly transferred into anitrogen filled glove box.

Photo-Active Layer Deposition

The photo-active layer was then coated from solution. The 1:(1-2) by wt.polymer:acceptor photo-active layer blends were prepared as 10-50 mg/mLsolutions in toluene, chlorobenzene, or trimethylbenzene. Solutions wereheated overnight at 80° C. Active layers were coated at 80-110° C. priorto coating. The hot solutions were deposited onto pre-heated ETL-coatedsubstrates via spin coating at 1600-3000 rpm for 40 seconds. Followingcoating the films were solvent annealed for at least 1 hour or thermalannealed at 80-120° C. for 1-15 min.

Hole Transport Layer Deposition

After the photo-active layer anneal, the substrates were loaded underinert atmosphere into the vacuum evaporator where MoO3 (HTL) and Ag (theanode) were sequentially deposited by thermal evaporation. Depositionoccurred at a pressure of 3×10−6 torr. MoO3 and Ag were deposited to athickness of 6 nm and 120 nm, respectively. The deposition rate for theMoO3 was 0.1-0.6 Å/s and Ag was 1.1-1.7 Å/s. Samples were then sealedwith the epoxy (EPO-TEK, OG116-31) and then cured in ELC-500 UV chamberfor 3 minutes at room temperature before testing in air.

Device Testing

Cells were tested under AM 1.5G 100 mW/cm² conditions with a NewportThermal Oriel 91192 1000 W solar simulator (4″×4″ illumination size).The current density-voltage curves were measured using a Keithley 2400source meter. The light intensity was calibrated with a crystallinesilicon reference photovoltaic (area=0.4957 cm²) fitted with a KG-5filter (calibrated by Newport to minimize spectral mismatch). Cells weremasked and an active area of 0.0656 cm² was measured. Light soakingstudies were performed on encapsulated devices installed with a UVfilter with a 385 nm cutoff.

Table 1 below list the HOMO, LUMO, and Bandgap levels of polymers.

TABLE 1 HOMO LUMO Bandgap Polymer (eV) (eV) (eV) Conventional Random−5.46 −3.78 −1.57 Copolymer Polymer A −5.37 −3.42 −1.95 Polymer B −5.35−3.40 −1.95 Polymer D −5.45 −3.49 −1.96 Polymer E −5.30 −3.35 −1.95Polymer F −5.23 −3.30 −1.93 Polymer G −5.48 −3.51 −1.96 Polymer H −5.54−3.58 −1.96 Polymer I −5.44 −3.50 −1.94 Polymer J −5.36 −3.41 −1.96

Table 2 below lists the OPV device performance for various polymer andacceptor blends.

TABLE 2 Polymer Acceptor PCE Voc FF Jsc Conventional Random BTP-4Cl-1210.4 0.786 69.2 19.2 Copolymer Polymer A BTP-4Cl-12 12.5 0.797 66.7 23.5Polymer B BTP-4Cl-12 10 0.805 62.6 19.9 Polymer D BTP-4Cl-12 10.7 0.80364.6 20.6 Polymer E EH-IDTBR 6.46 1.07 57.4 10.5 Polymer E BTP-4Cl-126.83 0.733 46.1 20.2 Polymer F EH-IDTBR 5.48 0.919 50.3 11.9 Polymer FBTP-4Cl-12 7.54 0.684 54.5 20.3 Polymer G BTP-4Cl-12 9.63 0.845 60.218.9 Polymer H BTP-4Cl-12 9.88 0.834 58.7 20.2 Polymer J BTP-4Cl-12 7.790.77 54.6 18.5

Jsc (mA/cm²) Short-circuit current density (Jsc) is the current densitythat flows out of the solar cell at zero bias. V_(oc) (V) Open-circuitvoltage (V_(oc)) is the voltage for which the current in the externalcircuit is zero. Fill factor percentage (FF %) is the ratio of themaximum power point divided by the open circuit voltage and the shortcircuit current. PCE (%) The power conversion efficiency (PCE) of aphotovoltaic cell is the percentage of the solar energy shining on aphotovoltaic device that is converted into usable electricity. EH-IDTBRis

and BTP-4Cl-12 is

Table 3 below describes the light soaking stability of PolymerA:BTP-4Cl-12 blends in OPV devices.

TABLE 3 Hours of PCE FF Jsc Voc Light Soaking (%) (%) (mA/cm2) (V) 012.5 66.7 23.5 0.797 250 11.6 64.3 22.1 0.786

FIG. 9 below describes three different polymer blends in terms of slotdie coating and thickness insensitivity.

In closing, it should be noted that the discussion of any reference isnot an admission that it is prior art to the present invention,especially any reference that may have a publication date after thepriority date of this application. At the same time, each and everyclaim below is hereby incorporated into this detailed description orspecification as an additional embodiment of the present invention.

Although the systems and processes described herein have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made without departing from the spirit and scopeof the invention as defined by the following claims. Those skilled inthe art may be able to study the preferred embodiments and identifyother ways to practice the invention that are not exactly as describedherein. It is the intent of the inventors that variations andequivalents of the invention are within the scope of the claims whilethe description, abstract and drawings are not to be used to limit thescope of the invention. The invention is specifically intended to be asbroad as the claims below and their equivalents.

The invention claimed is:
 1. A method comprising: reacting

with

to produce

wherein Y₁ and Y₂ are independently selected from the group consistingof: H, Cl, Br, I, and combinations thereof; wherein M is selected fromthe group consisting of H, trialkylstannane, boronate, or ZnX, wherein Xis Cl, Br, or I; wherein Z is a divalent linking group selected from thegroup consisting of:

and wherein R₁ is selected from: H, unsubstituted or substitutedbranched alkyls with 1 to 60 carbon atoms or unsubstituted orsubstituted linear alkyls with 1 to 60 carbon atoms.
 2. A method ofclaim 1, wherein R₁ is selected from 2-hexyldecyl or 2-octyldodecylalkane.
 3. The method of claim 1, wherein if Y₁ is H, Y₂ is Cl, Br, orI.
 4. The method of claim 1, wherein if Y₂ is H, Y₁ is Cl, Br, I.
 5. Themethod of claim 1, wherein at least M or Y₂ is H.
 6. The method of claim1, wherein if M is H, Y₂ is Cl, Br, I.
 7. The method of claim 1, whereinif Y₂ is H, M is trialkylstannane, boronate, or ZnX, wherein X is Cl,Br, or I.
 8. The method of claim 1, wherein

is

is

is


9. The method of claim 1, wherein

is

is

is


10. The method of claim 1, wherein

is

is

is


11. The method of claim 1, wherein

is

is

is


12. The method of claim 1, wherein

is further reacted to produce


13. The method of claim 12, wherein

is further reacted to produce


14. The method of claim 13, wherein

is further reacted to produce